• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.3
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• pp.315-321
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• 2001

Aerodynamic lenses are widely used in generating particle beams of high density and small diameter, but analytical or modeling studies are limited only in the free molecular regime. In this study, it is shown that generating particle beam is also possible in atmospheric pressure range, and the mechanism of generating particle beam using an orifice is analysed into three different parts : fluid dynamic contraction, diffusional defocusing, and inertial focusing. In laminar flow conditions, the diffusional defocusing effect can be neglected, and the effects of inertial focusing can be expressed in terms of the orifice size and Stokes number. Numerical experiments are done for two different orifices, d/D=1/5 and 1/10 and particle diameter d(sub)p=1-10 ㎛. The results for two different orifices can be made into a single curve when a modified Stokes number is used. The inertial focusing effect diminishes when the modified Stokes number becomes smaller than 10(sup)-2.

• The Korean Journal of Vision Science
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• v.20 no.4
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• pp.523-530
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• 2018

Purpose : The purpose of this study was to investigate the difference in the dynamic visual acuity between (DVA) the distance and near and the effect of change of accommodative stimulus on the dynamic visual acuity by the addition of the plus lens. Methods : The study involved 40 male and female adults ($22.84{\pm}2.43$ years old) with over 1.0 of visual acuity and without systemic disease or ocular disease. We compared the distance and near DVA and the change of DVA induced by the addition of the plus lens(+0.50D, +1.00D, +1.50D). Results : The distance DVA and near DVA are $78.86{\pm}19.46deg/sec$ and $76.90{\pm}18.05deg/sec$ respectively. The distance DVA was slightly higher(p=0.04). The higher the distance DVA, the higher the positive correlation with the near DVA and distance DVA, and distance DVA was higher in those who had higher the near DVA(r=0.95, p=0.00, Fig. 4). The near DVA according to the change of accommodative stimulus was $75.95{\pm}18.85deg/sec$ in full correction and the near DVA with +0.50D spherical power was $76.95{\pm}16.45$ but there was no statistically significant differences(p>0.05). However, the near DVA with +1.00D spherical power was $79.02{\pm}13.51deg/sec$ and it was slightly higher. Also, the near DVA with +1.50D spherical power was $84.28{\pm}18.96deg/sec$, there and it was statistically significant difference(p<0.05). Conclusion : There is no difference between distance and near DVA, but near DVA is also excellent if distance DVA is good. The DVA increases as added a plus lens for controlled accommodative stimulation changes.

• Journal of the Korean Society for Precision Engineering
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• v.32 no.9
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• pp.773-779
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• 2015

The laser Powder Bed Fusion (PBF) system is currently recognized as a leading process. Due to the various materials employed such as thermoplastic, metal and ceramic composite powder, the application's use extends to machinery, automobiles, and medical devices. The PBF system's surface quality of prototypes and processing time are significantly affected by several parameters such as laser power, laser beam size, heat temperature and laminate thickness. In order to develop a more elaborate and rapid system, this study developed a new PBF system and sintering process. It contains a 3-axis dynamic focusing scanner system that maintains a uniform laser beam size throughout the system unlike the $f{\theta}$ lens. In this study, experiments were performed to evaluate the effects of various laser scanning parameters and fabricating parameters on the fusion process, in addition to fabricating various 3D objects using a PA-12 starting material.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2009.01a
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• pp.601-605
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• 2009

We have proposed a measurement system for measuring a whole shape of an object easily. The proposed system consists of a camera and a cylinder whose inside is coated by a mirror layer. A target object is placed inside the cylinder and an image is captured by the camera from right above. The captured image includes sets of points that are observed from multiple viewpoints: one is observed directly, and others are observed via the mirror. Therefore, the whole shape of the object can be measured using stereo vision in a single shot. This paper shows that a prototype of the proposed system was implemented and an actual object was measured using the prototype. A method based on a pattern matching which uses a value of SSD (Sum of Squared Difference), and a method based on DP (Dynamic Programming) are employed to identify a set of corresponding points in warped captured images.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.788-793
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• 2002

Hybrid type slim tilt actuator and 6-wire supported are developed for DVD recording in the optical disc drive of notebook PC, which can compensate the inclination of disc and objective lens. The hybrid actuator uses the actuating method of moving coil in the focus and track direction and that of moving magnet in the tilt direction. Comparing with 6-wire supported actuator and hybrid type actuator, we can choose an actuator for slim super combo pickup. Two actuator are designed through the modal analysis and magnetic field analysis and experimental results shows dynamic characteristics. Finally, it is verified that the actuator can compensate the disc tilt of ${\pm}0.4^{\circ}$.

• Journal of Information Technology Applications and Management
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• v.17 no.3
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• pp.191-211
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• 2010

Existing models of knowledge processing do not feature a systemic meaning of knowledge management and ignore the role of leadership and social energy in the knowledge processing system (KPS). This conceptual paper introduces the Leadership Invigorating Flows of Energies, (LIFE) Model as an attempt to remedy that situation and provide a more useful description of the KPS. The LIFE Model highlights the role of emergent leadership and flows of social energies as forces encouraging knowledge creation and dynamic diffusion within an organization through the Knowledge Processing Cycle in eight activities interacting with its social knowledge base in a self-organizing system.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.101.3-101
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• 2001

By setting a refractor with a certain angle against the optical axis of the CCD camera lens, the image of a measuring point recorded on the image plane is displaced by the corresponding amounts related to the distance between the camera and the measuring point. When the refractor that keeps the angle against the optical axis is rotated physically at high speed during the exposure of the camera, the image of a measuring point draws an annular streak. Since the size of the annular streak is inversely proportional to the distance between the camera and the measuring point, the 3D position of the measuring point can be obtained by processing the streak. In this paper, for one of the applications of our system, the measurement of a moving surface is introduced. In order to measure the moving surface, multi laser spots are projected on the surface of object. Each position of ...

• Journal of the Korean Society for Precision Engineering
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• v.22 no.8 s.173
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• pp.151-158
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• 2005

In the semiconductor and the optical industry, a new transport system which can replace the conventional sliding systems is required. The sliding systems are driven by the magnetic field and conveyer belts. The magnetic field nay damage semiconductor and the contact force may scratch the optical lens. The ultrasonic wave driven system can solve these problems. In this paper, an object transport system using the excitation of ultrasonic wave is proposed. The experiments for finding the optimal progressive frequency and the phase-differences between two ultrasonic wave generators are performed. The relationships between transportation speed and the excitation frequency, flexural beam shapes and amplification voltage are investigated.

• Knowledge Management Research
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• v.4 no.2
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• pp.55-77
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• 2003

In this study, some issues that are related to embody the original conception and ideal of action learning are explored in terms of misunderstanding and misuse of action learning in Korean corporate context. The conception of action learning is deconstructed through the lens of 'action' and 'learning' concept, followed by conceptual analysis to the nature of 'action' and 'learning'. Based upon this conceptual deconstruction of 'action' and 'learning', this study is conducted to categorize the concept of 'action' and 'learning' into several representative attributes. Categorization of 'action' and 'learning' leads to draw some adjectives, for examples, reflective, dynamic, complex, nonlinear, that are critical for characterizing action learning. That is, the nature and ideal of action learning are critically reviewed with the reconceptualization of 'action' and learning, which are deconstructed. The Discussion of final thoughts is on what kinds of knowledge perspectives action learning holds in comparison with those of knowledge management and on how to facilitate knowledge construction and sharing with action learning.

• Journal of Information Technology Applications and Management
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• v.18 no.1
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• pp.15-39
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• 2011

A deeper understanding of how organizations behave as social complex adaptive systems is needed. In this paper we demonstrate how the Leadership Invigorating Flows of Energies model can help with this understanding. The model highlights the role of emergent leadership as a force encouraging the creation, diffusion, and utilization of knowledge through self-organizing mechanisms. We illustrate our approach by examining Wikipedia and show how it can be described as a social CAS. Our analysis of Wikipedia describes how emerging intrapreneurship behaviors result in dynamic flows of knowledge and self-organizing feedback mechanisms across the organization. We provide implications for organization studies and present evidence to support claims made by advocates of complexity theory. We conclude by proposing that Wikipedia can be seen as a new form of organization, and finish with a brief note highlighting a possible way forward.